In California it is illegal to remove the catalytic converter. Any honest inspection station will not pass a car without one. Applicable California laws that I found are: www.leginfo.ca.gov/cgi-bin/displaycode?section=veh&group=27001-28000&file=27150-27159 CALIFORNIA VEHICLE CODE: 27156. (a) No person shall operate or leave standing upon any highway any motor vehicle which is a gross polluter, as defined in Section 39032.5 of the Health and Safety Code. (b) No person shall operate or leave standing upon any highway any motor vehicle which is required to be equipped with a motor vehicle pollution control device under Part 5 (commencing with Section 43000) of Division 26 of the Health and Safety Code or any other certified motor vehicle pollution control device required by any other state law or any rule or regulation adopted pursuant to that law, or required to be equipped with a motor vehicle pollution control device pursuant to the National Emission Standards Act (42 U.S.C. Secs. 1857f-1 to 1857f-7, inclusive) and the standards and regulations adopted pursuant to that federal act, unless the motor vehicle is equipped with the required motor vehicle pollution control device which is correctly installed and in operating condition. No person shall disconnect, modify, or alter any such required device. (c) No person shall install, sell, offer for sale, or advertise any device, apparatus, or mechanism intended for use with, or as a part of, any required motor vehicle pollution control device or system which alters or modifies the original design or performance of any such motor vehicle pollution control device or system. (d) If the court finds that a person has willfully violated this section, the court shall impose the maximum fine that may be imposed in the case, and no part of the fine may be suspended. www.arb.ca.gov/bluebook/bb99/hs26/43008.htm CALIFORNIA HEALTH and SAFETY CODE: 43008.6. (b) The state board may collect a civil penalty not to exceed one thousand five hundred dollars ($1,500) for each violation of Section 27156 of the Vehicle Code. Any penalties shall be paid to the Treasurer for deposit in the Air Pollution Control Fund. (c) The civil penalty specified in subdivision (b) may be collected for one or more violations involving the tampering with or disabling of a gasoline-powered vehicle's air injection, exhaust gas recirculation, crankcase ventilation, fuel injection, carburetion, ignition timing, or evaporative control system, fuel filler neck restrictor, oxygen sensor or related electronic controls, or catalytic converter, or for the use of leaded fuel in a vehicle certified for the use of unleaded fuel only. Hank